Elbow prosthesis

Abstract

A prosthetic joint kit, particularly well suited for an elbow, transmits load through the prosthetic joint through a pair of spherically shaped bearing surfaces so as to transmit load over a relatively large area rather than at a point or over a line of contact. The prosthetic joint kit may be configured in a modular manner wherein a plurality of interchangeable stem structures, bearing structures and/or bearing inserts of various types are available. Construction in this manner enables a surgeon to configure the prosthetic joint to best suit the needs of the patient. For example, the surgeon may employ a modular flange for compressing a bone graft, a tissue fastener for securing soft tissue to a portion of the prosthetic joint, a cam for limiting the amount by which the prosthetic joint articulates or a bearing insert for tailoring the degree of varus/valgus constraint.

1. A prosthetic elbow kit comprising:
 a first stem structure having a proximal end and a distal end, the proximal end adapted to fit within a medullary canal of a humerus, the distal end terminating at a pair of furcations; 
 a first bearing component having a pair of slotted apertures and first and second condyle portions, each of the slotted apertures slidingly engaging one of the pair of furcations, each of the first and second condyle portions having a first spherically-shaped bearing portion which collectively define a first bearing surface; and 
 a second stem structure having a proximal end and a distal end, the distal end of the second stem structure adapted to fit within an ulna; 
 a second bearing component coupled to the proximal end of the second stem structure, the second bearing component including a pair of second spherically-shaped bearing portions that collectively define a second bearing surface configured to mate with the first bearing surface. 
 
     
     
       2. The prosthetic elbow kit of  claim 1 , wherein the first bearing component further includes a pin portion, the pin portion intersecting each of the first spherically-shaped bearing portion and coupling the first and second condyle portions together. 
     
     
       3. The prosthetic elbow kit of  claim 2 , wherein the first bearing component is unitarily formed. 
     
     
       4. The prosthetic elbow kit of  claim 2 , wherein at least one of the first and second condyle portions includes a pin aperture sized to receive the pin portion. 
     
     
       5. The prosthetic elbow kit of  claim 2 , wherein the second bearing component includes a through hole sized to receive the pin portion. 
     
     
       6. The prosthetic elbow kit of  claim 2 , wherein each of the first and second condyle portions is formed from a material selected from a group of materials consisting of polyethylene, cobalt chromium alloy, stainless steel, pyrolytic carbon and ceramics. 
     
     
       7. The prosthetic elbow kit of  claim 1 , further comprising a flange structure for releasably engaging one of the first and second stem structures, the flange structure being configured to fixate a bone graft and compress the bone graft against the one of the first and second stem structures. 
     
     
       8. The prosthetic elbow kit of  claim 7 , wherein the flange structure is fixedly but releasably engaged to the one of the first and second stem structures. 
     
     
       9. The prosthetic elbow kit of  claim 8 , wherein a threaded fastener is employed to fixedly but releasably couple the flange structure to the one of the first and second stem structures. 
     
     
       10. The prosthetic elbow kit of  claim 7 , wherein at least a portion of the flange structure is resiliently biased toward the one of the first and second stem structures. 
     
     
       11. The prosthetic elbow kit of  claim 1 , further comprising a tissue fastener for engaging one of the first and second stem structures, the tissue fastener being adapted to couple a soft tissue to the one of the first and second stem structures. 
     
     
       12. The prosthetic elbow kit of  claim 1 , wherein the first and second stem structures are hingedly coupled together when the first and second bearing surfaces are mated together. 
     
     
       13. The prosthetic elbow kit of  claim 12 , wherein the second bearing component is fixedly coupled to the second stem structure. 
     
     
       14. The prosthetic elbow kit of  claim 12 , further comprising a third bearing component which is interchangeable with the second bearing component, the third bearing component having a lateral buttress adapted for receiving a capitellum of the humerus. 
     
     
       15. The prosthetic elbow kit of  claim 12 , further comprising a third stem and third and fourth bearing components, the third stem having a proximal end and a distal end, the distal end of the third stem adapted to fit within a medullary canal of a radius, the third bearing component couple to the proximal end of the third stem and defining a third bearing surface, the fourth bearing component being interchangable with the first bearing component, the fourth bearing component having a pair of slotted apertures, first and second condyle portions and a lateral extension, each of the slotted apertures slidingly engaging one of the pair of furcations, each of the first and second condyle portions having a first spherically-shaped bearing portion which collectively define a first bearing surface, the lateral extension adapted to replace at least a portion of a capitellum of the humerus, the lateral extension defining a fourth bearing surface configured to mate with the third bearing surface. 
     
     
       16. The prosthetic elbow kit of  claim 15 , wherein a least a portion of each of the third and fourth bearing surfaces is spherically shaped. 
     
     
       17. The prosthetic elbow kit of  claim 15 , wherein the first bearing surface supports the second bearing surface for pivotal movement thereon in an unlinked manner whereby the first and second stem structures are not hingedly coupled. 
     
     
       18. The prosthetic elbow kit of  claim 1 , wherein the second stem structure is a threaded fastener. 
     
     
       19. The elbow kit of  claim 1 , wherein one of the first and second stem structures includes a cam structure with a tip, the tip being configured to contact the other one of the first and second stem structures to limit an amount by which the second stem structure can be rotated relative to the first stem structure. 
     
     
       20. The elbow kit of  claim 1 , wherein each of the slotted apertures of the first and second condyle portions is a depression formed in a substantially planar exterior end wall of the first and second condyle portions, having an abutment wall operable to engage one of the pair of furcations as the furcation is slid into one of the slotted apertures, and a passage through a sidewall at the exterior end of the first and second condyle portions sized to allow sliding passage of the furcation into the depression;
 wherein the first spherically-shaped bearing portion is a curved end wall that is curved and opposed to the substantially planar exterior end wall of each of the first and second condyle portions. 
 
     
     
       21. The elbow kit of  claim 20 , further compositing:
 a pair of bores, wherein each of the first and second condyle portions defines one of the pair of bores; and 
 a pin operable to be positioned in the pair of bores to couple the first and second condyle portions; 
 wherein the pin is operable to extend through a through bore defined by the second bearing component when coupling the first and second condyle portions; 
 wherein the first spherically-shaped bearing portion is operable to engage the second bearing component and the slotted apertures are operable to slidingly engage the pair of furcations when the first and second condyle portions are coupled with the pin. 
 
     
     
       22. A prosthetic elbow kit comprising:
 a first stem structure having a proximal end and a distal end, the proximal end adapted to fit within a medullary canal of a humerus, the distal end terminating at a pair of furcations; 
 a first bearing component having a pair of slotted apertures and first and second condyle portions, each of the slotted apertures slidingly engaging one of the pair of furcations, each of the first and second condyle portions having a first convex spherically-shaped bearing portion that has an apex on a first axis that is substantially perpendicular to a second axis of each slotted aperture, wherein collectively the first convex spherically-shaped bearing portion of both the first and second condyle portions define a first bearing surface; and 
 a second stem structure having a proximal end and a distal end, the distal end of the second stem structure adapted to fit within an ulna; and 
 a second bearing component coupled to the proximal end of the second stem structure, the second bearing component including a pair of concave spherically-shaped bearing portions that collectively define a second bearing surface configured to mate with the first bearing surface; 
 wherein each slotted aperture is defined by a first passage in an exterior sidewall and a second passage in an exterior end wall of the first and second condyle portions; 
 wherein one furcation is operable to slide into the slotted aperture through the first passage. 
 
     
     
       23. The prosthetic elbow kit of  claim 22 , wherein the first bearing component further includes a pin portion, the pin portion intersecting each of the first convex spherically-shaped bearing portions to couple the first and second condyle portions together. 
     
     
       24. The prosthetic elbow kit of  claim 22 , wherein the pin is positioned between the first and second condyle portions along the first axis. 
     
     
       25. The prosthetic elbow kit of  claim 24 , wherein the second bearing component defines a bore sized to allow the pin to pass through the bore;
 wherein the first and second condyle portions are operable to be connected with the pin extending through the bore in the second bearing component and the slotted apertures of the first and second condyle portions are operable to allow the pair of furcations to slide into engagement with the first and second condyle portions. 
 
     
     
       26. The prosthetic elbow kit of  claim 25 , wherein each of the pair of second concave spherically-shaped bearing portions include a first concave bearing surface defined around a first center axis and a second concave bearing surface defined around a second center axis at an angle to the first center axis;
 wherein each of the pair of second concave spherically-shaped bearing portions is configured to engage one of the convex spherically-shaped bearing portion of the first or second condyle portions. 
 
     
     
       27. A prosthetic elbow kit comprising:
 a first stem structure having a proximal end and a distal end, the proximal end adapted to fit within a medullary canal of a humerus, the distal end terminating at a pair of furcations; 
 a first bearing component, including,
 a first condyle portion extending along a first axis having a first side defining a first slotted aperture, wherein the first slotted aperture is a depression in an end wall of the first condyle portion that defines a second axis non-parallel to the first axis and a second side extending along the first axis away from the first side defining a first convex spherically-shaped bearing portion being convex along the first axis away from the first side, and 
 a second condyle portion extending along a third axis having a third side defining a second slotted aperture, wherein the second slotted aperture is a depression in an end wall of the second condyle portion that defines a fourth axis and a fourth side extending along the third axis away from the third side defining a second convex spherically-shaped bearing portion being convex along the third axis away from the third side, 
 wherein the first convex spherically-shaped bearing portion and the second convex spherically-shaped bearing portion collectively define a first bearing surface; 
 
 a second stem structure having a proximal end and a distal end, the distal end of the second stem structure adapted to fit within an ulna; and 
 a second bearing component coupled to the proximal end of the second stem structure, the second bearing component including,
 a pair of opposed concave spherically-shaped bearing portions that collectively define a second bearing surface configured to mate with the first bearing surface. 
 
 
     
     
       28. The prosthetic elbow kit of  claim 27 ,
 wherein each of the pair of opposed concave spherically-shaped bearing portions have a base defining a plane; 
 wherein each of the pair of opposed concave spherically-shaped bearing portions defines an apex point furthest from the plane; 
 wherein the apex point of each of the pair of opposed concave spherically-shaped bearing portions is the point nearest the other of the pair of opposed concave spherically-shaped bearing portions. 
 
     
     
       29. The prosthetic elbow kit of  claim 27 , wherein each of the pair of opposed second concave spherically-shaped bearing portions include a first concave bearing surface defined around a first center axis and a second concave bearing surface defined around a second center axis at an angle relative to the first center axis;
 wherein each of the pair of second concave spherically-shaped bearing portions is configured to engage one of the first or second convex spherically-shaped bearing portions defined by the first or second condyle portions. 
 
     
     
       30. The prosthetic elbow kit of  claim 27 , further comprising a lateral buttress;
 wherein the lateral buttress extends laterally from either of the first bearing component or the second bearing component; 
 wherein the lateral buttress is operable to receive the capitellum or replace the capitellum. 
 
     
     
       31. The prosthetic elbow kit of  claim 27 , further comprising:
 a cam structure with a tip defined by the second stem structure extending proximally from the second stem structure; 
 wherein the first stem structure defines a cross-bar between the pair of furcations; 
 wherein the tip is operable to contact the cross-bar to limit an amount which the second stem structure can be rotated relative to the first stem structure.